The proposed research is designed to determine if high expression alleles of macrophage inhibitory factor (MIF) are associated with the development of severe malarial anemia, and to characterize the mechanism whereby MIF suppresses erythropoiesis in the setting of malaria. Infection by P. falciparum results in 1-2 million deaths a year, mostly in African children under the age of five. Death occurs from the complications of infection, which include a severe and refractory anemia. Recent attempts to develop a malaria vaccine in primates also have been hampered by severe anemia after vaccination and challenge infection. The pathophysiology of these anemias is unknown. We have discovered that MIF is expressed in high levels in many malaria-infected individuals, suppresses erythroid progenitor development, and antagonizes erythropoietin signaling. MiF's action thus reflects the clinical analysis of many patients with severe malarial anemia. The objective of this application is to identify the pathogenetic basis for high MIF expression and the mechanism by which MIF interferes with the development of erythroid progenitor cells. The central hypothesis is that severe malarial anemia is the result of genetic predisposition to overproduction of MIF coupled with MIF's capacity to suppress erythropoiesis by inducing sustained activation of the ERK-1/2 MAP kinase cascade. We have formulated this hypothesis on the basis of our experimental studies showing first, that MIF is expressed in the blood and bone marrow during malaria infection, second, that there exists a polymorphism within the promoter of the Mifgene that affects its level of expression and third, that MIF inhibits erythroid progenitor development. The specific aims of the proposed research are: 1) Define the Frequency of Low Expression (5-CATT) and High Expression (6-, 7-, 8-CATT) Mif Alleles in Patients with Severe Malarial Anemia and Appropriate Controls, and Determine if the High Expression Alleles are Associated with Severe Anemia, and 2) Define the Pathways Responsible for the Suppression of Erythropoiesis during Malaria Infection. We expect to establish that there is over-representation of high expression in patients with severe malarial anemia, and to define the intracellular mechanism by which MIF sustains ERK-1/2 activation and interferes with erythropoietin action. These results will be significant because they will provide a more precise understanding of the molecular pathways responsible for severe malarial anemia.